///////////////////////////////////////////////
// Programovanie LPT v Linuxe - priklad c. 3 //
//                www.jariq.sk               //
///////////////////////////////////////////////

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/io.h>

#define EXIT_SUCCESS 0
#define EXIT_FAILURE 1
#define BASEPORT 0x378

int vytazenie_cpu(void);
void rozsviet_led(int usage);


int main(void)
{

    // Ziskanie prav pre pristup k portu
    if (ioperm(BASEPORT, 3, 1))
    {
        perror("Nepodarilo sa ziskat pristup k LPT");
        exit(EXIT_FAILURE);
    }

    // Hlavny cyklus programu
    while (1)
    {
        rozsviet_led(vytazenie_cpu());
        sleep(1);
    }

    // Uvolnenie prav pre pristup k portu
    if (ioperm(BASEPORT, 3, 0))
    {
        perror("Nepodarilo sa uvolnit pristup k LPT");
        exit(EXIT_FAILURE);
    }

    exit(EXIT_SUCCESS);

}


// Funkcia na zistenie vytazenia CPU
// -----------------------------------------------------------------------
// Funkcia je zalozena na kode aplikacie wmcpuload, ktorej autorom
// je Seiichi SATO <ssato@sh.rim.or.jp> a je sirena pod GNU/GPL licenciou.
// Principialne je tato funkcia vysvetlena aj na adrese
// http://www.experts-exchange.com/Programming/
//        Programming_Platforms/Linux_Programming/Q_20734330.html
// -----------------------------------------------------------------------
int vytazenie_cpu(void)
{
    
    int user, nice, system, idle;
    int used, subtotal;
    static int prevused, prevsubtotal;
    float usage;

    FILE *fr;
    
    if (!(fr = fopen("/proc/stat", "r")))
    {
        perror("Nepodarilo sa otvorit subor /proc/stat");
        exit(EXIT_FAILURE);
    }
    
    if ((fscanf(fr, "%*s %d %d %d %d", &user, &nice, &system, &idle)) == EOF)
    {
        perror("Nepodarilo sa precitat udaje zo suboru /proc/stat");
        exit(EXIT_FAILURE);
    }
    
    if ((fclose(fr)) == -1)
    {
        perror("Nepodarilo sa zatvorit subor /proc/stat");
        exit(EXIT_FAILURE);
    }

    used = user + system + nice;
    subtotal = user + nice + system + idle;
    usage = (100 * (double)(used - prevused)) / (double)(subtotal - prevsubtotal);

    prevused = used;
    prevsubtotal = subtotal;

    usage = (int) usage;
    return usage;

}


// Funkcia na rozsvietenie diod v zavislosti od hodnoty parametra usage
void rozsviet_led(int usage)
{
    
    if (usage <= 10)
    {
        outb(1, BASEPORT);
        outb(11, BASEPORT+2);
    }
    
    if ((usage > 10) && (usage <= 20))
    {
        outb(3, BASEPORT);
        outb(11, BASEPORT+2);
    }
    
    if ((usage > 20) && (usage <= 30))
    {
        outb(7, BASEPORT);
        outb(11, BASEPORT+2);
    }
    
    if ((usage > 30) && (usage <= 40))
    {
        outb(15, BASEPORT);
        outb(11, BASEPORT+2);
    }
    
    if ((usage > 40) && (usage <= 50))
    {
        outb(31, BASEPORT);
        outb(11, BASEPORT+2);
    }
    
    if ((usage > 50) && (usage <= 60))
    {
        outb(63, BASEPORT);
        outb(11, BASEPORT+2);
    }
    
    if ((usage > 60) && (usage <= 70))
    {
        outb(127, BASEPORT);
        outb(11, BASEPORT+2);
    }
    
    if ((usage > 70) && (usage <= 80))
    {
        outb(255, BASEPORT);
        outb(11, BASEPORT+2);
    }
    
    if ((usage > 80) && (usage <= 90))
    {
        outb(255, BASEPORT);
        outb(10, BASEPORT+2);
    }
    
    if (usage > 90)
    {
        outb(255, BASEPORT);
        outb(8, BASEPORT+2);
    }
    
}